1. Field of the Invention
The present invention relates to a light-emitting device including a plurality of files arranged in parallel, each having a plurality of light-emitting elements which are arranged in a mounting area on which the light-emitting elements are mounted and which are connected in series to each other.
2. Description of the Related Art
In recent years, light-emitting sources each including a plurality of arranged light-emitting elements have been used as light-emitting sources for illumination. As the light-emitting elements, light-emitting diode elements (LED elements) are often employed because it has a less power consumption and a long operating life for lighting. Because the LED elements are a point light source, it is required that a plurality of LED elements is used to be arranged to satisfy a request for desired brightness or light-emitting range necessary to light sources for illumination. In a light-emitting device in which a plurality of LED elements are arranged, if the number of the arranged LED elements is large, there is a case where the LED elements are formed in a group unit or block unit in which some LED elements are packed (for example, see JP2011-014836A and JP2010-287657A).
A light-emitting device disclosed in JP2011-014836A has a configuration in which a plurality of LED element groups each having a plurality of LED elements arranged is connected in parallel with each other. Each LED element group is composed of LED elements of different number. A connection manner of a first LED element group and a second LED element group to a power source is configured to be changed such that a resistance value obtained by combining values of the first LED element group and the second LED element group depending on a source voltage is varied. In addition, the connection manner of the LED element groups are performed by exchanging a voltage supplied from the power source selectively.
On the other hand, JP2010-287657A discloses a light-emitting module in which a plurality of light-emitting elements is arranged in light-emitting areas. The light-emitting module includes a plurality of light-emitting areas and a plurality of electrodes. LED elements of the number depending on a size of each light-emitting area are connected in series in the light-emitting area, and a voltage is supplied to the light-emitting area through a pair of electrodes for power-feeding of the plurality of electrodes. The pair of electrodes for power-feeding includes a pair of power-feeding terminals between which a supply power is connected.
As mentioned above, although some LED elements are arranged by dividing them in a plurality of element arrays, a source voltage supplied to the plurality of element arrays is performed by the pair of electrodes for power-feeding. However, if lighting is driven by pair of electrodes for power-feeding, because a common voltage is supplied to all of the LED element arrays, the entire brightness is constantly maintained, but it is not easy to limit partially light-emitting areas or brightness.
In JP2011-014836A, the brightness or light-emitting arrays can be adjusted by providing a switch element or resistance element on each LED array unit. However, parts of the switch element or resistance element and so on other than the LEDs are required. On the other hand, in JP2010-287657A, if the brightness is adjusted, it is necessary to adjust variably the source voltage connected between the pair of power-feeding terminals.
In this way, the conventional light-emitting devices using the LED elements does not disclose a structure to light LED elements in one or more files independently and to light LED elements in files as a block. in a predetermined array unit. In particular, if a plurality of LED elements is arranged in an area, there is no existing light-emitting device in which LED elements are arranged and lighting can be controlled so that brightness can be adjusted in a stepwise fashion in a state where entire lighting balance is maintained.